How are extra field values handled when creating a contract?

App Development
1

I was asked the following:

If we send extra data that’s not defined in a template schema what is supposed to happen? For example, say we have a template that defines a structure:

{
   "foo": string,
}

and we provide a payload to ledger of:

{
    "foo": "bar",
    "other": "other data",
}

Will ledger ignore “other” or throw an error?

2

Using Canton 2.10.0, that depends on whether you are submitting to the Ledger API (gPRC) or the JSON API.

The Ledger API responds with:

COMMAND_PREPROCESSING_FAILED:
Expecting 3 field for record... but got 4

The JSON API ignores the extra fields.

3

Using Canton 3.3.0-snapshot.20250319.0, the situation is a bit different.

The Ledger API responds with:

COMMAND_PREPROCESSING_FAILED:
Found non-optional extra field "note",
cannot remove for downgrading.

The Ledger JSON API responds with:

INVALID_ARGUMENT:
The submitted request has invalid arguments:
Unexpected fields: note